The goal of this proposal is to advance our understanding of the fundamental molecular mechanisms involved in the formation of dental enamel, with an emphasize on the nanoscale structure and function of the proteins of the secretory stage enamel matrix and its contained arrays of amelogenin "Nanospheres." We postulate that such understanding will lead to the future development of biomimetic strategies for the creation of enamel-like mineral materials. Our general hypothesis is: Amelogenin primary structure defines amelogenin quaternary structures (nanospheres) which in turn direct enamel matrix supramolecular architecture facilitating the postnucleation growth of carbonated hydroxyapatite enamel crystals. This biomineralization process is affected through two major molecular mechanisms: (1) amelogenin-protein interactions resulting in the organization of the enamel extracellular matrix and defining the spatial environment, and, (2) protein-mineral interactions, inhibiting premature crystal-crystal fusion and promoting the controlled and oriented growth of the enamel crystals. We propose to examine this hypothesis with the following Specific Aims: 1. Using recombinant and native enamel proteins (amelogenins, enamelins and ameloblastin), to identify the nature of the interactions which define protein self-assembly in solution and the nanosphere matrix architecture, at the molecular level. 2.Using recombinant and native enamel proteins to define, at the supramolecular level, the ultrastructural architecture of amelogenin-gel matrices formed in vitro in the presence and absence of enamelins and ameloblastin proteins. 3. To characterize apatite and octacalcium phosphate crystal growth, morphology and orientation within synthetic amelogenin gel matrices in the absence and presence of the non-amelogenins. 4. To characterize the effects of amelogenin and non-amelogenins on apatite and octacalcium crystal growth morphology in solution, determining the nature of molecular interactions of the proteins with these calcium phosphate crystals. 5. To define, at the supramolecular level, the ultra structural architecture of amelogenin-gel matrix in vivo and to determine the localization of enamel proteins and their relation to the mineral phase. In summary, considering tooth enamel as a tissue that may be restored with biomimetic strategies, it is envisaged that the knowledge and information gained from these proposed studies will provide the inspiration for material scientists to design and develop novel and improved biomaterials.